
#region Apache Notice
/*****************************************************************************
 * $Revision: 405046 $
 * $LastChangedDate: 2008-10-19 05:25:12 -0600 (Sun, 19 Oct 2008) $
 * $LastChangedBy: gbayon $
 * 
 * iBATIS.NET Data Mapper
 * Copyright (C) 2008/2005 - The Apache Software Foundation
 *  
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 ********************************************************************************/
#endregion

using MyBatis.DataMapper.Model.Sql.Dynamic.Elements;
using MyBatis.Common.Utilities.Objects;
using MyBatis.Common.Utilities.Objects.Members;

namespace MyBatis.DataMapper.Model.Sql.Dynamic.Handlers
{
	/// <summary>
	/// Summary description for IsNullTagHandler.
	/// </summary>
	public class IsNullTagHandler : ConditionalTagHandler
	{

        /// <summary>
        /// Initializes a new instance of the <see cref="IsNullTagHandler"/> class.
        /// </summary>
        /// <param name="accessorFactory">The accessor factory.</param>
        public IsNullTagHandler(AccessorFactory accessorFactory)
            : base(accessorFactory)
		{
		}

		/// <summary>
		/// 
		/// </summary>
		/// <param name="ctx"></param>
		/// <param name="tag"></param>
		/// <param name="parameterObject"></param>
		/// <returns></returns>
		public override bool IsCondition(SqlTagContext ctx, SqlTag tag, object parameterObject)
		{
			if (parameterObject == null) 
			{
				return true;
			}
		    string propertyName = ((BaseTag)tag).Property;
		    object value;
		    if (!string.IsNullOrEmpty(propertyName) ) 
		    {
		        value = ObjectProbe.GetMemberValue(parameterObject, propertyName, AccessorFactory);
		    } 
		    else 
		    {
		        value = parameterObject;
		    }
		    return (value == null);
		}
	}
}
